In known processes of this type (DE-B-3 414 437) the treatment takes place through mechanical scutching and hackling, i.e. beating and combing of the fibers. More specifically, the flax fibers are clamped and then treated by means of hackling combs with the result that wood constituents and the like are removed while the fibers are aligned parallel to one another. The bast is then divided into long fibers, which are kept clamped and aligned in parallel, and into so-called tow. The tow consists of very short fibers which are combed out of the clamped long fibers and removed.
From the combined long fibers, a yarn is usually produced in subsequent treatment steps. The yarn is then processed, for example, to form textile materials. The long fibers continue to contain wood constituents and other impurities to a certain extent, in particular being unbleached.
The long fibers produced by hackling cannot be mixed with short fibers of other materials, say cotton, to form mixed yarns. This is because the machines used for wet spinning of long fibers cannot process such a fiber mixture, in addition to these machines working very slowly. The long fibers are therefore processed without the addition of other fibers to form a roving or finished yarn. The roving, which has acquired a certain strength and fiber adhesion through a first spinning step, is usually cleaned and bleached. In comparison, a cleaning of the finished yarn is more difficult because the cleaning liquor penetrates the finished yarn much more poorly than the roving.
The tow produced during the treatment by hackling is either directly processed to form relatively coarse yarns or carded in such a way that short fibers form (so-called cottonizing). The short fibers are used unbleached for the manufacture of yarns or fleeces. If the tow is subjected to a washing and bleaching process, such as flock or batch cooking, a mass of cleaned and bleached short fibers forms. This mass, however, is very matted, and in some cases the fibers are twisted or entwined with one another. It is therefore not possible to directly produce from this mass a fiber structure that can be processed further to make filaments, other than through strong mechanical tearing. However, such tearing leads to substantial waste and to fiber shortening.
It is also already known (DE-A-3 923 498) to delignify and prepare flax by passing it through mechanical treatment stations in several steps. The flax fibers, which have already been mechanically pre-treated, are brought into a degree of parallel alignment with the help of needle-bearing conveyor belts. The treated and aligned fibers are then stacked via other conveyor belts to give a fiber hank.
The fiber hank obtained in this way contains a mixture of long fibers and short fibers, in addition to still containing wood constituents and other impurities. The fibers, aligned in longitudinal direction and parallel to one another, initially have practically no bond whatsoever with one another. This is because the needles of the conveyor belts all circulate in the same direction and at essentially the same rate of feed, thus merely aligning the neighboring flax fibers in the direction of feed without forming a bond between neighboring fibers. This bond is achieved only by following conveyor belts which, in addition to their feed motion, also create a degree of cross movement of the flax fibers, thereby intending to form fiber bundles. However, this does not result in a noteworthy bonding of neighboring fibers.
It is also known (DE-A-1 927 043) to collect wool to form a fiber strip which is then subjected to a steam treatment to remove grease that is present. This steaming can take place during various stages of the treatment of the fiber strip. This treatment process usually includes stretching operations, but can also include brushing and combing, to obtain a fiber strip which can be processed to give a wool yarn. However, such a process is not suitable for the preparation of sclerenchyma fibers, in particular flax, because the sclerenchyma fibers present in the fiber strips produced by customary treatment processes are too stiff and not fine enough.